Insulating compound and process of making the same.



"r .r s A'rns r 'rEN moron.

EMILE HEMMING, F PASSAIC, NEW JER$EY, ASSIGNOR TO HEMMING- MANUFAC- TUBING COMPANY, OF GARFIELD, NEW JERSEY, A CORPORATION OF NEW JERSEY.

rnsurnrme ooivrrounn AND raocnss or MAKING 'rnn SAME.

This invention relates to substances of the.

character described in Miiller Patent- No. 869,321 adapted especiallyfor' electrical insulating purposes and composed of asbestos and a resinous or bituminous material such as coal tar pitch. One of the greatest recommendations of such a composition is that it yields a satisfactory insulating substance from inexpensive materials capable of being shaped, pressed, or molded, in a cold state, followed by drying or heating to drive ofi' the volatile constituents. I

The shaping of the articles in a cold or cool condition permits a large output from a' small number of molds, since the article-does not have to cool in the mold, and the insulating and heat-resisting properties of the article are much superior to those of materials manufactured under the hot-molding process. Cold molding on the other handrequires a high degree of care and skill in the selection and compounding of the materials. The method of preparing the plastic binder, as heretofore practised, while it yields a merchantable article if skilfully executed, has been somewhat slow, wasteful in the use of solvent, and not readily adaptable-to working in large batches or' over a considerable period of time because of the evaporation of the solvent and the resultant difliculty of maintaining a uniform degree of plasticitysuited to the molding operation. Furthermore, the attainmentof a roper condition of plasticity in the binder so ely b V the use of a volatile 'solventsuch as benzo substantially precludes the employment of heat as an. aid in reducing the pitch to a liquid consistency, and the finished article derives no substantial strength or density from the solvent itself.

It is the object of my invention to im rove upon the aforesaid process and articlia, or those of a like nature,'and I accomplish this by substituting for a part or the whole of the benzol or other volatile solvent/used in the preparation of the binder, anthracene.

oil, namely the distillate of coal tar which Specification of Letters Patent.

Patented May t, 1912.

Application filed April 12, 1911. Serial No. 620,548.

passes over at temperatures above 270 C. or thereabout. The oil used may either be ord nary anthracene oil or the refined oil remaining after the valuable product anthracene has been extracted therefrom, which residue is sometimes known as lubricating oil, and it may either be used alone or in company with a suitable proportion of benzol; but not.being a ready solvent of the pitch at ordinary temperatures, like benzol, the melting or .liquefying is preferably accomplished with the aid of heat. f

In carrying out the invention I may take, by way of example, about 55 parts by weight of asbestos, preferably ground, and 45 parts of a binder composed of moderately hard coal tar pitch and anthracene oil in the, proportion of-2 to 1 by weight, or the solvent as stated may contain a greater or less propor-- tion of benzol to increase its fluidity and promote the admixture of the asbestos with the binder. These proportions may be varied somewhat according to the conditions or the qualities desired in the product.

The pitch and the solvent containing or composed of anthracene oil are mixed, pref erably with the aid of heat, as in a steamjacketed vessel, resulting in a thick liquid which is added to the asbestos, and these ingredients are then thoroughly intermixed by any suitable means, the object being to obtain a loose or substantially granular mass slightly lumpy in texture. When benzol alone or any analogous oil is employed as a solvent for the pitch, it tends to pass off during the process of intermixing the asbestos with the binder, which takes considerable time, .and the resulting substance is somewhat too granular or powdery to attain the greatest desirable density of texture in the molded article and hardness in the completed product, unless more solvent is added or the mixture is. immediately intro-,

and the material does not lend itself to proper molding.

After the asbestos and binder have been prepared and'thoroughly intermixed according to my invention,- a suitable quantity thereof may be placed in a mold of the desired form without heating, and subjected to heavy pressure, after whichthe molded article may be immediately removed and subjected to the drying or baking process, the latter being preferably started at a relatively low heat, which is gradually raised to a temperature of substantially 200 C. The anthracene oil, after evaporation, appears to leave a residue of its own in the product, increasing the strength and density of the latter.

I claim,

1. The herein-described composition of matter possessing high electrical insulating properties and comprising a hard, baked, molded-,mass composed of asbestos, coal-tar pitch, and a non-volatile residue of anthracene oil.

2. The herein-described process which consists in preparing a binding mixture of coal tar pitch and anthracene oil, mixing the same with powdered asbestos to a slightlylumpy granular consistency, compressing the mixture in a mold, and baking the molded article.

3. The hereindescribed process which consists in preparing a binding mixture of coal tar pitch and anthracene oil with the aid of heat, mixing the same with powdered asbestos in the proportion of substantially 15 parts .of asbestos to 55 parts of the binder, and molding the resulting material in a cold condition.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses, this eleventh day of April, 1911.

EMILE HEMMING. Witnesses:

R. M. PIERSON, G. BLAKE. 

